Useful Linux commands

This page will contain some useful Linux commands.

Vocabulary – in the UNIX/Linux world directory is a special type of file that contains a list of objects (files or other directories). Folder and directory are interchangeable terms. Directories are organized in a tree structure. The highest in the chain is ‘/’ (root directory).

ls - (list) – list the contents (files and directories) of a directory. If no directory path is specified it defaults to your working directory. Some useful arguments:

• ls -l displays the permissions, user and group ownership, and date of creation in addition to displaying the contents.
• ls doesn’t display hidden files by default (.<filename> - if a filename starts with dot, then it is not visible). ls -a shows you hidden files too.

mkdir - (make directory) – creates a new directory.

cd - (change directory) – change your working directory to a specified path. If no path is provided, then it brings you to the previous working directory.

• Useful shortcuts – cd .. (“cd out”) – brings you to the parent directory of your current working directory.
• cd ~ - your home directory
• cd / - here the path is / so it brings you to the root directory.

pwd – (print working directory) – prints the full path of your current working directory

rm - (remove) – deletes files. If you want to delete a folder use rm -r option.

cp <source_file_path> <target_file_path> (copy)- make a copy of a file. (use -r option for folders)

mv –(move)- move a file to a new location. This command is also often used to rename files.

vi/nano/emacs – file editors – also helps you create new files.

diff –(difference) - you can provide this command with two files and it will compare them line by line. If these files are identical then the output will be empty.

cat – (concatenate) – displays the contents of a file to stdout.

grep – searches text data for lines that contain some string.

head – display

whoami – displays your username

history – display your command line history clear – clears your terminal window

chown – change owner of a file/directory

chmod – change permissions of a file/directory

chgrp – change group ownership of a file/directory

passwd – change your password

echo – pring a string to stdout

sudo – run a command with root permissions

su – (substiture user) - change the user

apt/yum – package managers

hostname – display the name of a host (machine you’re working on)

exit – exit the terminal

date – display date/time

mount, df, ps(pstree), awk, sed, head, tail, ln, alias, scp, ssh, wget, find, which, locate, chown, man, tar, ifconfig, ping

Piping('|')

Keyboard Shortcuts:

Tab - autofill the file or directory name currently being typed

Up/down arrows - go through the history of commands you have typed

Ctrl + C - end the command that is currently being executed (useful for getting out of a place where it keeps asking you to enter something and you don't want to)